1. Field of the Invention
The present invention relates to synchronous signal/active signal restoring apparatus and method, and more particularly, to a synchronous signal/active signal restoring apparatus and method in which a display device receives a digital image signal transmitted in an optical signal form from a source device through an optical cable, a physical medium which can not transmit a clock signal, and restores a horizontal/vertical synchronous signal and a horizontal/vertical active signal.
2. Description of the Background Art
In line with the development in electronic technology, a flat panel display (FPD) device has been developed and increasingly adopted as a display device such as a television receiver or a monitor to display an image, instead of a voluminous, large and heavy CRT.
The flat panel display device is classified into a device using an inorganic substance and a device using an organic substance. The device using the inorganic substance includes a PDP (Plasma Display Panel) using a PL (Photo Luminescence) and an FED (Field Emission Display) device using a CL (Cathode Luminescence). The device using an organic substance includes an LCD (Liquid Crystal Display element) and an organic EL (Electro-Luminescence) display device.
Among them, the PDP, since the advent of a large-scale PDP, is commonly adopted as a display screen of a display device such as the television receiver and the monitor because it has a high luminescence, a high-luminescence efficiency and a wide view angle, and can be fabricated at a low cost compared to other flat display device, has excellent heat-resistance, cold-resistance and dust-proof characteristics, easily implements a full color, and is light-weight.
In addition, the display device employing the PDP as a display screen is light-weight and thin, so that it has been developed also as a wall-mount type.
In order to output an image or a voice, an image signal or a voice signal outputted from a source device such as a set top box is inputted to the display device. For an image and voice output of the display device, conventionally, various cables are connected between the display device and the source device, so that an image signal or a voice signal of the source device is transmitted to and received from the display device through the cables, and a control signal is also transmitted and received between the display device and the source device through the cables.
Transmission and reception of an image/voice signal or various control signals transmitted and received between the display device and the source device through the cable will now be described.
FIG. 1 is an exemplary view showing connection relation between the display device and the source device in accordance with a conventional art.
Reference numeral 100 denotes a wall-mount type display device such as a wall-mount type monitor or a wall-mount type television receiver using the PDP as a display screen.
Reference numeral 110 is a digital device such as a digital VTR (Video Tape Recorder) or a DVD (Digital Video Disc) player outputting a transport packet stream corresponding to digital image signal and voice signal by reproducing a certain reproduction medium.
Reference numeral 120 is an analog device such as a VTR or a computer system outputting an analog image signal and voice signal by reproducing a reproducing medium such as a video tape.
Reference numeral 130 is a source device such as the set top box which receives a digital broadcast signal, receives the transport packet stream from the digital device 110 and the analog image signal and voice signal from the analog device 120 and selectively switches them, and transmits the switched signal to the display device 100.
In the conventional apparatus, plural digital devices 110 and the source device 130 are connected by a cable such as an IEEE 1394 cable, and the digital device 110 outputs the transport packet stream corresponding to a digital image and voice signals obtained by reproducing a certain reproducing medium. The outputted transport packet stream is transmitted to the source device 130 through the IEEE 1394 cable
The analog device 120 and the source device 130 are connected by a coaxial cable. The analog device 120 reproduces a certain reproduction medium and generates an analog image signal, analog R, G, B signal or an analog voice signal. The generated analog signals are transmitted to the source device 130 through the coaxial cable.
The source device receives a digital broadcast signal by means of an internal ATSC (Advanced Television Systems Committee) tuner, and converts the transport packet stream corresponding to the received digital broadcast signal and the transport packet stream inputted from the digital device 110 into an analog image signal and an analog voice signal.
And then, the source device selectively switches the converted analog image signal and the analog voice signal, and the analog image signal and the voice signal inputted from the analog device 120, and transmits them to the display device 100. At this time, the source device 130 transmits the analog R,G,B signal and the analog voice signal of channels L and R to the display device 100 through each cable.
Between the display device 100 and the source device 130, an additional control/response cable is connected, through which a control signal and a response signal according to the control signal are transmitted.
However, the conventional art has the following problems. That is, because the display device 100 and the source device 130 are connected by several cables, if the display device 100 is installed on a wall as a wall-mounted type and the source device 130 is installed on a shelf, the cable for transmitting the analog R,G, B signal and the analog voice signal and the cable for transmitting the control signal and the response signal to the control signal are exposed at the wall exposed between the display device 100 and the source device 130. The exposed cable is not good for appearance.
Therefore, instead, the display device 100 and the source device 130 may be connected by one thin optical cable which can be hardly recognized at a distance. Then, the source device 130, the source device 130 converts an image signal, a voice signal, a control signal, image signal characteristics and voice signal characteristics into an optical signal and transmits it to the display device through an optical fiber, and the display device 100 receives and processes the optical signal.
In order for the source device 130 to transmit various signals in an optical signal form to the display device 100 through the optical fiber, a 8 bit data should be converted into a 10 bit data so as to be suitably transmitted, and the optical signal should be converted into a predetermined format of serial data because the optical signal can not be transmitted as a parallel data.
Thus, the source device 130 selects various signals in order of a predetermined format, encodes them, converts the 8 bit parallel data into 10 bit data, converts again the 10 bit parallel data into serial data, and then transmits them in an optical form through the optical fiber.
FIG. 2 shows a format structure of a serial data having image/voice/control signal and image/voice signal characteristics in a packet form transmitted from the source device to the display device.
A reference numeral 200 is an image signal packet with the largest data capacity. The image signal packet 20 includes include one horizontal line of image signal. As for a header of the image signal, if the image signal is a blanking section, a blanking header is formed, whereas if the image signal is the active section, an active header is formed. And a tail is successively formed behind the image signal.
Between the image signal packets 200, there are positioned a voice signal packet 202, a control signal packet 204, an image signal characteristic packet 206 and a voice signal characteristic packet 208, and a header and a tail are formed ahead and behind each packet. The packets positioning order may be changed.
The serial data with such a format structure is encoded and then converted into a 10 bit data suitable for optical signal transmission, and converted into an optical signal in an optical signal transmitter, and transmitted to the display device 100 through an optical fiber.
At this time, the optical fiber, a physical medium for transmitting the optical signal, is not able to transmit a clock signal that the source device 130 has used to process an image signal, to the display device 100.
Even though a clock signal is not inputted from the source device 130, the display device 100 may judge an approximate frequency of a clock signal for restoring an image signal through an image signal characteristic packet received from the source device 130 and generate a clock signal with the judged approximate frequency.
However, the clock signal generated by the display device 100 can not be the same as the clock signal used in the source device 130, it is not possible to restore accurate horizontal/vertical synchronous signal and horizontal/vertical active signal.